Visual programming is a computer programming technique that allows for rapid development of visually oriented programs (visual programs). FIG. 1 is a diagram illustrating a sample operation of a visual program. The visual program is a temperature converter, which converts Fahrenheit to Centigrade, and vice versa. The Fahrenheit scroll bar 101 is used to set the Fahrenheit value to between 0 and 100 degrees as indicated by the position of the Fahrenheit slider 103. The Fahrenheit display 102 displays the numeric Fahrenheit value represented by the position of the Fahrenheit slider. The Centigrade scroll bar 111 is used to set the Centigrade value between 0 and 100 degrees as indicated by the Centigrade slider 113. The Centigrade display 112 displays the numeric Centigrade value represented by the position of the Centigrade slider. In operation, when the Fahrenheit slider is moved by a user, the Centigrade slider is automatically moved to the corresponding Centigrade position and the Fahrenheit and Centigrade displays are updated. Conversely, when the Centigrade slider is moved by a user, the Fahrenheit slider is automatically moved to the corresponding Fahrenheit position and the Centigrade and Fahrenheit displays are updated.
Visual programming allows various components (e.g., a scroll bar) to be interconnected visually to effect the program behavior. A visual programming environment typically includes a list of predefined components that can be interconnected to create a visual program. Each component may include input and output ports and a visual interface. When creating a visual program, a programmer specifies the visual components and their location on the display. The programmer also specifies the interconnection between various ports. The components pass values through these connections. FIG. 2 is a block diagram illustrating a scroll bar component. The scroll bar component 201 receives messages from the operating system (e.g., mouse down) and controls the display of a scroll bar. The scroll bar also provides an input port 203 and an output port 202. The input port is used to receive a value indicating a new position of the slider and the output port is used to send a value indicating a new slider position. The scroll bar can be connected to other components through its ports.
FIG. 3 is a diagram illustrating a scroll bar connected to a display component. A display component 301 has one input port 303 for receiving a value. The display component controls the displaying of the value that it receives. The output port 202 of the scroll bar component 201 is connected to the input port 303 of the display component. In operation, whenever the scroll bar slider is moved, a value indicating the new position of the slider is sent from the scroll bar component to the display component. The display component receives this value and updates its display accordingly.
Although prior references have described general visual programming environments, visual programming is not widespread because of the inefficiencies of visual programs. For example, visual programs often execute in an interpretive mode that results in unacceptably slow performance.